Shields come with Shield (Rating), but I don't see that stat being calculated anywhere.

Forums say that it increases Shield CHANCE, but shields always have base 5% chance regardless of shield's rating.

Comparing two shields, one with 50 rating and other with 60, have no difference, other than stats that come with their mods.

Can someone clarify this for me?

I'm not understanding the question...

Are you asking how Shield Rating is applied (or calculated) in comparison to chance?

I'm not understanding the question...

 

Are you asking how Shield Rating is applied (or calculated) in comparison to chance?

To make it simple - what is Shield Rating?

Since it's not shield chance, nor defense rating, nor absorption rating.

Looking at every possible stat and it's calculation, ie. defense = armor + buffs, I can't find what shield rating does!

Shield rating is a stat that you find on gear, just like power, alacrity, Willpower, Endurance, etc. You're not going to see it in appreciable amounts until you hit your mid-30s, which is why I'm guessing you have no idea what it is.

The item rating of your shield is not the same as shield rating. The item rating on your shield only affects the amount of Tech or Force Power provided; regardless of item rating, shields all have the exact same default shield chance (5%) and default absorb value (20%). Shield rating, which can be found on pretty much anything and everything, except for bracers and belt, is a stat that increases your chance to shield (for moddable gear, it's only present on your Enhancements).

When referring to the ratings, if you're curious how much you have, just hover your cursor over the relevant chance in your Character Sheet tab; you'll see a breakdown of the various contributions to the stat (rating, buffs, baseline). You can do the same to any of the relevant entries on your character tab.

That's because the "Shield (Rating X)" number at the top of the tooltip isn't used for anything, other than relative quality compared to other shield generators. To make things even more confusing, you can get items that have a "+x Shield Rating" as one of their stat bonuses, along with Endurance, Aim, and/or whatever else. This doesn't affect the "Shield (Rating xx)" on your shield generator, but does affect your Shield Chance.

Found it.